Glyoxylate Reductase Activity in Pea Leaf Protoplasts Nucleotide Specificity and Subcellular Location

Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

“…The preferential localization of HPRs and GRs in the bundle sheath cells, where most of the glycolate metabolism occurs (13,33), seems consistent with the involvement of these activities in the oxidative photosynthetic carbon pathway, as has been proposed for the reductases from C3 species (11,13,(16)(17)(18)32). It is generally accepted that the enzyme compartmentation, metabolite transport and the sequence of reactions from P-glycolate up to the level of glycerate in the bundle sheath tissue are analogous to those found in C3 species (13,22,26,33 peroxisomes is most probably directly involved in the photorespiratory cycle, utilizing hydroxypyruvate derived from serine by the action of another peroxisomal enzyme, serine:glyoxylate aminotransferase (13).…”

“…HPR-2 is localized largely in the cytosol ( 16) and, in analogy to the peroxisomal reductase, shows nonspecific rates with glyoxylate (18). NADPH(NADH)-GR is also mostly cytosol based (11,16), it is specific for glyoxylate (19), and should be considered as an important glycolate-generating reaction in leaves (17,19,20). Both enzymes have been proposed to serve as back-up reactions of the glycolate pathway, utilizing glyoxylate and hydroxypyruvate generated in the peroxisomes and 'leaked' or otherwise exported to the cytosol (1 1, [16][17][18][19][20].…”

The Enzymic Reduction of Glyoxylate and Hydroxypyruvate in Leaves of Higher Plants

“…Chloroplast GR activity has generally been found to have a maximum activity of only 3 to 6 ,mol mg-' Chl h-1, and this has been confirmed by several recent studies (3,15,25). In contrast, crude whole-leaf extracts of spinach contain nearly 10-fold higher glyoxylate-reducing activity per unit Chl than do preparations of purified intact chloroplasts (3,9,11).…”

“…In contrast, crude whole-leaf extracts of spinach contain nearly 10-fold higher glyoxylate-reducing activity per unit Chl than do preparations of purified intact chloroplasts (3,9,11). This is not what would be expected if GR were located solely in chloroplasts.…”

“…3,22) and by immunochemical localization studies (18). HPR-1 is highly active in leaves (see Table I) and has a clear preference for hydroxypyruvate over glyoxylate (14); the reduction of hydroxypyruvate is freely reversible.…”